The present invention relates to telemetering systems, and particularly to telemetering systems designed to transmit information from the bottom of a borehole to the surface while drilling the borehole. The present invention is particularly useful in hard wired telemetering system in which the data transmission length from the bottom of the well to the surface consists of a hard wired electrical circuit. A system of this type is disclosed in U.S. Pat. No. 3,696,332. The hard wired system described in this patent utilizes special drill pipe in which each section of the drill pipe is provided with an electrical conductor that extends through the section. Special contact rings are imbedded in the sealing shoulders of the tool joints at each end of the section. Thus, when the drill pipe sections are joined, the mechanical and electrical connections are made simultaneously, and the electrical circuit is completely isolated from both the interior and exterior of the drill pipe. While the patent discloses a special drill pipe that can be used to transmit data from the bottom of the well to the surface of the well while the well is being drilled, it does not disclose a means for continuing the electrical circuit through the surface. Normally, the surface equipment will comprise a saver sub, a lower kelly cock, a kelly and an upper kelly cock, all of which is suspended from the swivel of the drill rig.
The present invention is directed to providing a means for extending the circuit formed by the specialized drill pipe of the above patent through the surface equipment to slip rings disposed on the upper end of the kelly, upper kelly cock, or swivel sub. U.S. Pat. No. 3,989,330 discloses a means for extending an electrical circuit through a kelly cock assembly. This patent discloses an electrical circuit which is formed by a conductor placed to one side of the kelly cock which terminates in contacts that are centered in the ends of the kelly cock body. While this is one possible means for extending an electrical circuit through a kelly cock, it has a serious disadvantage in that the electrical conductor and contacts are not isolated from the fluid in the interior of the kelly cock. Thus, the electrical circuit is exposed to the drilling fluids which flow through the kelly cock and the possibility of damage to the electrical circuit exists.
In addition, U.S. Pat. No. 4,016,943 discloses an apparatus similar to that disclosed in U.S. Pat. No. 3,989,330 for extending a circuit through a kelly. The system disclosed comprises a conductor disposed in the center of the bore of the kelly and exposed to the drilling mud. The connector at the ends of the conductor are positioned in the ends of the kelly and serve to connect the conductor to the other equipment. When the necessity to run wireline tools through the drill string arises, the connector and conductor must be removed. Once removed, they cannot be reinstalled until the drill string is removed from the borehole.